Alcanbrad

So we have been having ghost shifting issues with our recent upgrade to SRAM etap on our Co-Mo where when we are under low low speed high torque climbing, the chain attempts to climb out of the current gear riding on top of the cassette cog only to snap loudly back into place with a noticeable forward jerk in the pedals. I am working through the issues and solutions for the ghost shifting (I may start a separate thread here as the thread I started in the bike mechanics forum didn't yield and valuable comments), however, we are a heavy team (>400lbs) that rides in very hilly terrain and not being familiar with 11 drive trains yet, and given the behavior I described, I am very nervous about the chain snapping.

Searching this forum, all the threads about chain strength are quite old and out of date.

I have seen 11 speed chains advertised for ebike claiming they are stronger to take the added torque an ebike would generate and am thinking that, for piece of mind, this would be a good way for us to go.

Has anyone had experience with, or have anecdotal stories about the use of an 11 speed ebike chain in a tandem environment?

Also, any experience with 11 speed chains snapping on a tandem? Suggestions/advice?

TIA

WheelsNT

Nothing on 11 speed, but we did just replace the drive chain on our 9-speed Co-Mo quad. I elected to go with a KMC e-bike chain, thinking that the stronger the better. We’ve had no issues. Helpfully, the e-bike chains come 136 links long instead of the usual 116, so I was able to make the chain two links longer than we had been using which should put less stress on the derailleur if I make a mistake and end up in the big-big combo. I don’t do this intentionally, but mistakes happen sometimes.

Another thing I realized is that every chain manufacturer specifies the weight of their chain. When I was racing, I paid attention to reducing weight. Now on a tandem, I recently realized that I probably ought to find the heaviest chain I can. Of course there’s more to chain strength and reducing wear (“stretch”) than weight, but data like alloy metallurgy and heat treatment are not usually published in specifications for chains. Weight, on the other hand, is, so it’s easy to just find which chains use more metal.

tandem rider

An interesting study on chain friction and wear. Do long wearing chains have more strength?

https://zerofrictioncycling.com.au/chaintesting/

oldacura

May not be related but I have used SRAM chains on most of our bikes. I like the quick link better than the Shimano solution. On my mountain bike (10 speed I think) I've had an issue recently that sounded like "chain suck": Occasionally, the chain would hang up on a cog tooth, ride part way around before it would let go and snap back into place. I could rarely catch it because it occurred only occasionally. What I think I discovered is that the quick link was hanging up on the adjacent (larger) chainring and not disengage when it should (at 6 o'clock).

Is it possible that you are experiencing a similar situation on the cassette where the quick link is catching the adjacent (larger) cog, riding up with it before releasing and falling back onto the current cog? Can you have your Stoker watch as the quick link comes around? Might you color the quick link a contrasting color (like with a Sharpie) so you can see it more readily?

OneIsAllYouNeed

Most likely, you're feeling the results of chainstay flex. In your lowest gear combination, the chain tension is highest, so you're most likely to bend the chainstays. With eTap, you can microtrim individual gears to compensate for wonky behaviors like you're experiencing. It doesn't address the root cause, but you should be able to tune that gear to keep the chain from jumping.

A stiffer chain won't necessarily help, but it can't hurt. KMC X11e is a solid choice.

Alcanbrad

Thanks folks, I will probably replace the SRAM Red22 chain with an ebike chain. Piece of mind, no, the stokers piece of mind is important to address.

the behavior is most interesting, only in the small chainring and second to largest cog. I don’t think (but I don’t know for sure) the chain is climbing onto the larger cog, I think the chain is climbing out of the second cog by the inner link climbing on top off a tooth (not a link plate riding up a ramp) (everything is brand new)

i can write a short novel covering everything I have done and just made another major setup change that we’ll try this weekend. I’ll start a separate thread after learning what this does. I’m to the point where I still have some money, but I am out of places to throw it 🤔

CliffordK

So far I've never broken a 11s chain.

My last few chains were Wippermann 11sx chains from https://www.bike-discount.de/

The peening on the pins was so tough that it bent my chain tool trying to remove a pin... Or was that a Wippermann 9s chain?

I have looked at the KMC X11e e-bike chains, but haven't tried one yet.

Trevtassie

This^^^^^ Wippermann chains are bomber...especially the ebike chains like the 11SE.

LV2TNDM

I don't think chain strength is the issue here. It isn't snapping or bending, right? If not, it's a meshing problem which would be caused by alignment problems.

I think the chainstay flex suggestion may be part of the problem. The other issue that wasn't mentioned is chainline. If your chainline is not ideal, when your chain is in the LEAST amenable position for your bike, it will be most likely to suffer issues under load. In other words, if you have bad chainline and then are torquing with high loads and flexing your stays, your chainline then gets so bad that you're now derailing your chain. I'm guessing this is the problem.

However, you have to eliminate other obvious causes first: chain/cog (or cassette) mesh issues. Was one recently replaced and the other not? Then, stiff chain link? Then, bent chain link? Chain links are easily twisted. They twist when shifting under load. A tandem puts tons of load on a chain, plus captain and stoker don't always time shifts perfectly. So check your chain by pedaling and looking down the length of the chain to spot any twists. Also check for a bent chainring tooth. Or cog tooth. This is rare, but not beyond the realm of possibility.

So if you eliminate all other potential drive train skip culprits, then I'd guess it's a frame alignment or chainline issue. Are your chainrings centered between your cogs? If they're too far off center, you have a chainline issue. Also, is this problem caused by cross-shifting? 11 and 12 speed systems are stretching the bounds of good drive train mesh, so you may simply be having problems based on this.

Another potential problem would be derailleur alignment. Is your hanger straight, resulting in the derailleur hanging perpendicular to the axle as well as aligned parallel to the centerline of the bike? If there's any twist, this would result in mis-aligned pulley wheels which could cause chain mesh issues. Check that derailleur hanger's position. It should be perfectly aligned.

LV2TNDM

Great link. Thank you for posting. I haven't spent much time on their site, but objective evaluation of chain durability is badly needed. I hope their results are indeed objective and valuable.

But I simply have to take issue with this:
"Q-How often should I re wax?
A-I recommend approx. every 300km for normal road conditions and approx. 6 to 8 hours off road."

So ZeroFriction recommends rewaxing after every two to four off road rides? That right there is enough to convince me waxing chains is a COMPLETE WASTE OF TIME. I don't know about you, but I simply do not have the time or energy to follow the removal-heat wax-soak chain-hang to cool-reinstall process every two, three, or four rides. Just getting to my chain with a rag and lube bottle can be enough. Now multiply times four (for a family) and you'd need a separate kitchen just for chain cooking! This is just for four mountain bikes. Plus add road bikes and tandems, plus city/commuting bikes? I'd be a full time chain waxer if I followed this approach.

I assumed a waxed chain would last a month off road. But this short interval means I won't even consider waxing. Not enough time in the day. I'd rather spend my time riding than monitoring cups of hot wax & chains all over the house!!! I guess I should thank my lucky stars there are myriad chain lubes on the market for virtually all riding conditions.

bikeinxs

We run 11 spd chain as do a number of tandem friends. I've mentioned this before, but the worlds top pros ride regular 11 speed chains and they don't break them. Chain strength is not the issue.

CliffordK

Is there a need for the Captain to communicate to the Stoker when one is shifting? So, perhaps drop power slightly when shifting. Although, most of the new rings and cassettes are very good at picking up the chain for smooth shifting.

wtandem

Don’t forget to check S&S couplings for tightness if you have them. Not sure if it was the same issue, but years ago I had a little shifting issue and it was one coupling slightly loose.

LV2TNDM

Soft pedaling during shifts will reduce the chance of twisting and/or breaking a chain. Rear shifts are so smooth with Hyperglide-like ramps, cutouts and the like, that it's not as much of an issue today. But two mashers on the pedals crossing the chain over a few cogs can still do damage. Shifts between rings tend to need soft pedaling more. Communication can simply be saying "shift" a half or full second prior to needing to shift. This gives the stoker time to anticipate and let up. However, over time, a team will learn what cadence range they prefer and once it goes above or below ideal, the stoker knows a shift is coming. After enough time together, slightly letting up on the pedals is all that's needed to communicate a shift is forthcoming.

In general, shifts tend to be lighter and less harsh on the drivetrain on road. Off road, loaded shifting seems to be more of a problem and I tend to use "shift" more frequently.

I hope that helps.

Toespeas

could be a bend in your chain rings , maybe try a ten speed chain , sometimes you can just have a nic in the drive train and it will just never shift right until you swap it out !